Effect of single wall carbon nanotubes on human HEK293 cells
Daxiang Cui, Furong Tian, Cengiz Ozkan, Mao Wang, Huajian Gao., Effect of single wall carbon nanotubes on human HEK293 cells. Toxicology Letters, 2005. 155(1): p. 73-85.
Summary:
The biocompatibility of single-walled carbon nanotubes (SWCNTs) was studied using human embryonic kidney cells (HEK293). SWCNTs are said to hold great promise in biomedical engineering and medical chemistry because of their novel properties and promising applications. For example, SWCNTs can be functionalized with
The authors studied the effects of SWCNTs on HEK293 cells by performing cell viability, proliferation, and attachment assays. Similarly,
The above graph shows the decrease in cell viability (as a percentage compared to the control which contained no SWCNTs) on a day-to-day basis. Higher concentrations of SWCNTs meant lower starting cell viability percentages.
The above graph shows how cell adhesive ability decreased as a function of increasing SWCNT concentration and time. Western blot analysis showed time-dependent down-regulation of important adhesion-associated genes such as laminin, fibronectin, and collagen IV.
Cell apoptosis was induced by the presence of SWCNTs, which was accompanied by the up-regulation of certain apoptosis-associated genes. Also, at certain concentrations of SWCNTs, the cell cycle was arrested in the G1 phase. This result was accompanied by the down-regulation of cell cycle-associated genes such as cyclin D1 and cdk2. Again, both of these results were time- and dose-dependent.
It was observed that HEK293 cells responded to the presence of SWCNTs by secreting proteins in order to aggregate and wrap SWCNTs. Aggregates of SWCNTs and HEK293 cells gradually showed apoptosis while nearby cells continued to grow well. The observation demonstrated a possible cellular response mechanism to the foreign SWCNTs.
Significance:
This paper is important because it tested the effects of SWCNTs on human HEK293 cells and their basic functions. SWCNTs in the future may be used as drug delivery devices because of their small size and functionality in adsorption and binding of molecules such as
6 comments:
In regard to induced cell apoptosis due to the SWCNT's: did the study mention if the SWCNT itself caused apoptosis, or rather induced a cascade of cell signals that resulted in the cell apoptosis? To determine the exact cause of this would be a very useful study, as it could provide valuable information to not only the detailed effects of the interactions between SWCNT's and cells, but also to how they can be implemented to be effect drug deliverers.
Also, do you think it would be plausible to use the SWCNT's themselves as a 'cell killer,' per se? For example, if there was a benign tumor somewhere in the body, could SWCNT's be tweaked to be inserted and simply kill the tumor effectively? There are many treatments for this, so I'm wondering if SWCNT's could be an effective way to kill these tumors (as opposed to surgery, radiation therapy, etc.).
You mention that the SWCNTs could be used in drug delivery, was there any evidence of the cells physically uptaking the SWCNTs? Other than monitoring cell adhesion genes, and apoptosis, were there any other novel changes to the cells after being exposed to the SWCNTs? Since the cells were expressing more adhesion related genes, is there a critical concentration of SWCNTs in which there is increased cell adhesion without inducing apoptosis?
Seems like a classic case of bio-compatibility. Doing a bit of wiki, initial studies show CNT to be toxic causing symptoms such as inflammation, epithelioid granulomas, fibrosis, etc, and even possible carcinogenic.
Even in light of this, the properites of CNTs as a good biomaterials cannot be overlooked (durable, very small, absorbent, etc). I'm wondering whether there is a technique to coat the CNTs to nullify its toxicity so that it can be used as a biomaterial.
Shyam: The paper did not discuss exactly what led to apoptosis, just that the SWCNTs were cytotoxic and that there was a certain interaction that caused the cell death. It could possible be some sort of cell membrane breaking down and allowing the SWCNT into the cell that could further lead to the cell's death. A lot more research has to be done in terms of the biocompatibility. Some sort of lipid functionalized on the surface of the SWCNT may provide for increased biocompatibility. Similarly, this must take into account specificity as well if one wanted to target say a cancer cell and not a healthy cell.
Jeff: I'm not sure if there is exactly a specific critical concentration, however, I do know that SWCNTs can be functionalized by attaching small molecules to their surface. If you attach a ligand, the specific receptor on a cell would be able to take up the SWCNT with some specificity. This is thought of as a possible cancer therapy technique since some forms of cancer cells over-express certain receptors that healthy cells do not.
Tue: Similar to Jeff's question, there is research currently being done on new synthesis techniques to make these SWCNTs that might reduce their cytotoxic effects. Similarly, functionalizing the SWCNT surface with a small molecule may also improve biocompatibility by reducing the apoptotic effects of the SWCNTs.
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